Add heartbeat

models/events.py

@@ -179,6 +179,13 @@ class DTMFEvent(BaseEvent):
     digit: str = Field(..., description="DTMF digit (0-9, *, #, A-D)")
 
 
+class HeartBeatEvent(BaseModel):
+    """Server-to-client heartbeat to keep connection alive."""
+
+    event: str = Field(default="heartBeat", description="Event type")
+    timestamp: int = Field(default_factory=current_timestamp_ms, description="Event timestamp in milliseconds")
+
+
 # Event type mapping
 EVENT_TYPES = {
     "incoming": IncomingEvent,
@@ -198,6 +205,7 @@ EVENT_TYPES = {
     "metrics": MetricsEvent,
     "addHistory": AddHistoryEvent,
     "dtmf": DTMFEvent,
+    "heartBeat": HeartBeatEvent,
 }